Cutting torches are generally used for cutting metal by locally heating the metal to its oxygen ignition temperature with a preheat flame powered by an oxygen/fuel gas mixture and subsequently cutting the metal with a high velocity cutting oxygen stream supplied by the torch. The preheated metal is oxidized by the cutting oxygen, thereby releasing a considerable amount of thermal energy which further heats the surrounding metal. The high velocity oxygen stream physically removes the molten material by oxidation, thereby cutting the metal. Mixing a preheat fuel gas such as acetylene, propane, natural gas, etc., with preheat oxygen gas for preheat combustion may be accomplished either internally or externally of the torch. In the first case, mixing of the preheat gases occurs in a premix torch nozzle and in the second case the preheat gases are mixed by turbulence in the gas stream after exiting a postmix nozzle.
Larger flames may be achieved with postmix nozzles. Postmix nozzles are usually employed in industrial processes for cutting slab steel and the like. Thermal energy radiated from the preheat flame and the molten metal causes heating of a cutting torch, interfering with the handling of the torch and promoting the adhesion of molten cutting metal to the torch tip, sometimes blocking the gas exit openings in the nozzle and increasing the potential for flashbacks and other hazards. Therefore, cooling of cutting torches is desirable for improving their handling and performance and to increase their service life.
Water cooling systems for welding or cutting torches are known from Rehrig (U.S. Pat. No. 4,508,951) and published British patent application GB 2,189,670 by Musker. The Rehrig cooling system includes an annular cooling water conduit, which extends longitudinally of the torch body and is longitudinally separated into two equal chambers. The cooling water enters one of these chambers at the rear end of the torch, flows to the torch head where it enters the other chamber and exits that other chamber at the rear end of the torch. One disadvantage of this cooling arrangement is that the water is heated before it reaches the torch head, resulting in insufficient cooling of the torch head, the hottest part of the torch. Furthermore, since the inlet and outlet for cooling fluid are diametrically opposed on the torch butt, the torch body is unevenly cooled. This can result in uneven and inadequate cooling and possible damage to the torch due to thermal stress and potential warping.
In the cooling system taught by Musker, cooling water is directed through a plurality of passageways extending longitudinally in a cylindrical jacket of the torch body. The cooling water enters these passageways in one half of the jacket at the rear end of the torch body, flows through these passageways towards the head, and subsequently flows rearward from the head through the passageways in the other half of the jacket to the rear end of the torch body where it exits the torch. It is a disadvantage of such a water cooled torch that the water flow in the passageways will be of different velocity which leads to uneven cooling of the torch. It is a further disadvantage that the construction of the jacket is time consuming and involves costly manufacturing techniques. Furthermore, the cooling of the torch head is insufficient and the cooling of the torch body is uneven for the reasons discussed in relation to the cooling system taught by Rehrig.
The cooling efficiency of such a multi passageway system and the cooling of the torch head, may be improved by dividing the cylindrical jacket into two separate cooling jackets, which are each individually supplied with cooling water. However, in such a cooling system, uneven and unsatisfactory cooling of the torch still results and the cooling system becomes even more difficult and costly to manufacture.
These problems are overcome by the present invention which provides a cooling system for a fluid cooled cutting torch that effectively cools the torch head and evenly cools the torch handle or body, while being easily manufactured at low cost. Furthermore, prior art fluid cooled cutting torches are not adapted for use interchangeably with premix and postmix nozzles. The torch of the present invention may be readily converted from a premix torch to a postmix torch and vice versa. The torch of the present invention may further be used with a premix heating nozzle for heating purposes only.